A critical period in the sensitivity of basal forebrain cholinergic neurones to NGF deprivation.

CHOLINERGIC neurones of basal forebrain (BF) express receptors for nerve growth factor (NGF) and are sensitive to NGF. In many CNS structures, including the BF region, the expression of NGF and its receptors is developmentally regulated. To test whether BF neurones depend on NGF during restricted time windows of postnatal development, we antagonized endogenous NGF by implanting, in the lateral ventricle of the rat, hybridoma cells producing blocking antibodies specific for NGF. Implants were performed at postnatal day 2 (P2), P8 and P15. BF cholinergic neurones were drastically reduced in number only when endogenous NGF was antagonized during the first postnatal week. We conclude that BF cholinergic neurones are sensitive to NGF deprivation only during early postnatal development.